To perform a randomized controlled trial to assess the effectiveness and cost-effectiveness of lumbar fusion and use of instrumentation in the surgical management of patients with degenerative lumbar spinal stenosis. Specific aims of Development and Feasibility Study: (1) Design multicenter randomized controlled trial; in particular, establish consensus among surgeon co-investigators on criteria for randomization to fusion and to instrumentation; (2) Collect pilot data to document the feasibility of a multicenter randomized controlled study of spinal fusion and examine preliminary results.